How Do They Run Clinical Trials for Birth Control?

Aren't the subjects afraid of getting pregnant?

A clinical trial of a male contraceptive has been canceled, researchers announced Monday, after the drug was shown to induce serious side effects in 10 percent of the men who used it. Wait, how are subjects chosen for clinical trials of contraceptives? Aren't they worried about getting pregnant?

They're willing to take their chances. Scientists look for healthy, fertile, sexually active subjects who don't want to get pregnant or impregnate anyone, but understand there's a risk of conceiving. Most modern contraceptive trials involve several phases: In the early going, researchers try to evaluate the basic safety of their drugs, and the extent to which they can lower a man's sperm count or inhibit a woman's ovulation; later on, they measure the drug's real-world efficacy at preventing unwanted pregnancies.

In the early phases of testing, volunteers take the experimental drug while using other forms of contraception, like condoms or diaphragms. For later tests, participants are asked to forgo these backup methods, and are instructed to consider the attendant risks. (In the case of male contraceptives, researchers look for men in committed relationships who can discuss the risks with their partners.) In any case, researchers are pretty confident, at this point, that the new drug works about as well as other products in common use; they're just trying to compute its precise rate of efficacy, along with its ease of use and the extent of its side effects.

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Still, why would anyone take their chances with an experimental contraceptive? Some may be motivated by a desire to help develop new drugs. That's often the case in trials of male pills and injections, as many subjects believe that men should bear some of the burden for birth control. Male subjects may also be dating women who can't use other forms of contraception. As for women, the motivations are free health care and free birth control. And there's always the allure of cold, hard cash: Participants in these trials can earn a decent amount of money—maybe $1,000 or more, depending on the exact details of the experiment.

At least no one has to worry about getting a placebo. As a general rule, contraceptive trials test a new treatment only against itself. There's no need for a control group, since researchers know how individuals would fare with standard methods, or without any "treatment" at all. (About 85 percent of couples using no form of contraception get pregnant within a year.)

Explainer thanks John K. Amory of the University of Washington, Doug Colvard of CONRAD,Elaine Tyler May, author of America and the Pill: A History of Promise, Peril, and Liberation, Daniel R. Mishell Jr. of the Keck School of Medicine at University of Southern California, and Ronald Swerdloff of the Los Angeles Biomedical Research Institute at the Harbor-UCLA Medical Center. Thanks also to reader Mike Spitz for asking the question.

Maura Kelly is the author of Much Ado About Loving, about what classic novels can teach you about mating, relating, and Internet dating.